TEETH OF ARMADILLOS
complete the arcade. The preznaxillaries are very small, and are
usually lost in dried skulls. Coupled with these points of likeness
are some differences. The lower jaw, for instance, has a well-
marked coronoid process. The pterygoids do not meet in the
middle line. The teeth are five or four in each half of each jaw.
There is no trace of a second set.
A peculiarity of the Sloths is the enormous number of dorsal
vertebrae. There are twenty -three of these in Gholoepus hqffimanni,
but only fifteen to seventeen in the Three-toed Sloth, Bradypus.
As in other American Edentates, the acromion joins the coracoid.
This connexion occurs in both the Two- toed and the Three-toed
species. The limbs of these creatures are very long, a concomitant
of an arboreal life. The femur has no third trochanter. The
genus Bradypus, which by reason of the fact that it has not lost
the third toe on the manus seems to be more primitive than
Choloepus, shows another structural feature which does not bear
out this conclusion. The trapezoid and the os magnum of the carpus
are united, while in Clioloepus they are perfectly distinct bones.
The intestine has no caecurr,
There are several species of Sloths. Eminently perfect though
the organisation of the Sloth in relation to its particular sur-
roundings appears to us, Buffon selected the animal as the very
type of imperfection in nature. " One more defect/* he wrote,
" they could not have existed."
Fam. 3. Hasypodidae. — The family Dasypodidae or Arma-
dillos contains a considerable number of genera. Tatttsia, Toly~
peutes, Dasypus, JCenurus, Priodon,1 and ChlwmydopJwrus. They
have all a more or less rigid covering of bony plates imbedded in
the skin, which are not in the least comparable with the scales of
the Manis. Save the Whales, in one or two genera of which
traces of a dermal armature exist, the Armadillos are unique
among existing mammals in this particular. The term " Edentate "
is especially inapplicable to the Armadillos ; the genus Priodon
may have more than forty teeth in each jaw ; a total of ninety
was found in one specimen examined by Professor Kukenthal.
In the tendency of the teeth to multiply, we have anot"her
example of a state of affairs which characterises so many Whales.
Generally, however, seven to nine is the number of teeth in each
1 This name is "written ** Prionodos " by Gray, whlcli might lead to a confusion
with tlic Carnivore Prionodon.